Are you looking at being IATA accredited? If not all you need is to go for a course in travel agency management. This will enable you run your agency effectively, regardless of the IATA accreditation or not.

Get subscribed to the major GDS available i.e Sabre, Amadeus, worldspan.

In addition, make sure you have a solid business plan for whatever you want to do, so as to check the viability, before investing a dime. Also make sure you have at least basic knowledge of the industry, and flair and passion for marketing.